You should re-read the usage message for $Messagesvery carefully.
–
Brett ChampionFeb 1 '12 at 18:08

@Brett actually I didn't read it at all; I trusted Szabolcs. I blame him!
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Mr.Wizard♦Feb 1 '12 at 18:12

To clarify a bit the somewhat cryptic answer of @Brett - $Messages point to a channel, which can be a list of streams, but not a single stream without a list around it.
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Leonid ShifrinFeb 1 '12 at 18:13

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